The nipple or shank end of presently used hose coupling are disposed at a standard 15.degree. angle relative to the body of the hose coupling so as to allow the hoses to hang between the cars such that the engaged couplings are fully rotated to a fully engaged position. With certain type of railway cars, however, such as the long-underframe type, the coupled hoses assume a relatively horizontal disposition rather than a sagging disposition, in which case the coupling heads may not be fully rotated to a fully engaged position, that is, the engaged couplings are forced to partially rotate in a direction of uncoupling or disengagement. Consequently, any bounce of the hose or striking of the coupling by a foreign object may raise the coupling to a level sufficient for effecting uncoupling and an undesired emergency brake application.
In order to prevent untimely or undesired disengagement of the hose coupling, self-locking hose couplings having automatically latching mechanisms have been proposed. These designs have proven to be cumbersome, unreliable in disengagement, susceptible to freezing and considerably more costly to manufacture.
Also proposed, as a means of preventing untimely disengagement of hose couplings, is a coupling having a straight shank and an increased coupling lip angle. The straight shank was intended to force the couplings to be further rotated toward a fully engaged position, while the increased lip angle was intended to further assure coupling engagement over a wider range of rotation in the coupling direction. Subsequently, however, with the approval of usage of a "softer" hose, the straight shank coupling produced kinking of the hose and consequently restriction of air flow therethrough.